Well my first question to you would be, what are you looking for out of the truck? You will never get the $15,000 back out of your 2nd gen. Personally, i love the sound of the old 2nd gens, and i wish i would have hung onto my 12 valve, however the newer trucks will inheretently be more reliable. Less mileage, and upgraded suspension components on the new rigs are great. You also have to consider the emissions garbage. Personally, i would look for a decent 3rd gen....maybe an 06 or early 07 with the 5.9. I am not a huge fan of the new 4th gen trucks but many on here are. If you are looking for a truck to play with, keep what you got. If you are looking for a reliable daily driver, i would consider upgrading to newer...but not NEW to avoid the emissions stuff. Good luck!